Interengaging impeller fluid pump



March 1, 1949, I K. A. BEIER INTERENGAGING IMPELLER FLUID PUMP Filed Feb. 17, 1945 JNVENTOR. I KURT /7. 3470?. BY a HTTjK/VCTJ,

Patented Mar. 1, 1949 INTERENGAGING IMPELLER- FLUID PUMP Kurt A. Beier, Indianapolis, Ind., assignor to Schwitzer-Cummins Company,

Ind., a corporation.

Indianapolis,

Application February 17, 1945, Serial No. 578,411 7 Claims. (01. 103-126) This invention relates to a fluid pump of the type commonly known as the Root rotary blower and which may be primarily employed as a supercharger for pumping air to internal combustion engines or the like.

In the Root blower of conventional design, as each lobe of the involving rotors passes the edge of the usual rectangular outlet, the air which has been compressed at the outlet is free to rush back into the chamber between the following lobes with sudden force. This results in an uncontrolled pressure rise with a resultant noise due to the instant opening to the outlet exposing the entrapped air between the rotor lobes and the housing to the discharge pressure. Thus the sudden admission of the high pressure air to the low pressure area results in a pulsating effect, which is highly objectionable.

It is the purpose of this invention to so design and construct the pump or blower as to mate rially reduce this pulsating effect and noise by effecting a uniform rate of pressure rise of the entrappedair between the lobes. This is accom plished by providing a gradually widening orifice to allow the air to slowly pass from the high pressure, area to the low pressure area as the rotor lobes scan the outlet opening so that the pressure in the space following the lobes-will gradually rise to that of the outlet opening without sudden pulsations.

To effect a gradual equalization of pressure, a

leakage area is provided between the high pressure area of the outlet and the chamber formed between the rotors and housing by forming the housing with a secondary bore eccentric of the main bore whereby the rotors will gradually recede from the housing as they approach the outlet opening. Thus the leakage area between the high pressure outlet area and the chamber formed between the rotors and housing, at any rotor position relative to the housing, will be of such size that the pressure rise in the latter will take place at a substantially uniform rate with respect to rotor rotation.

The invention, therefore contemplates forming the housing of the rotors by providing a second bore of larger diameter than the primary bore and located eccentrically thereto, the eccentricity being oriented toward the main center line of the unit. The exhaust ports may also be made of such shape that they continue the control of uniform pressure rise. By means of this construction of the housing and the exhaust ports, a material reduction in the pulsating noise is accomplished. This same principle and structure is similarly applicable to the inlet opening and its ports depending upon the character of the pump or blower.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a perspective view of a fluid pump.

Fig. 2 is a central vertical section therethrough showing in dotted lines varying positions of the rotor lobes. r

Fig. 3 is a plan view of the exhaust or intake ports.

' Fig. 4 is a diagrammatic illustration of the form of housing relative to the path of the rotors.

In the drawings there is illustrated a fluid pump or Root blower comprising the housing I 0, dual driving shafts II and meshing driving gears [2 for driving the shafts II. On the shafts are keyed the rotors I 3 carrying the meshing lobes l4 whereby they are synchronized in their driving relation for rotation in the direction indicated by the arrows of Fig. 2. Upon rotation of the rotors, air is drawn into and entrapped between the rotor lobes through-the inlet opening indicated at I5 and is forced through the outlet opening indicated at "5.

Both the inlet and outlet openings embody a series of ports, as shown in Fig. 3, wherein there is provided plates l'l inserted or cast integral with the housing and curved inwardly toward the center in continuation of the curvature of the adjacent wall of the housing and formed with walls 18 and a strut l9. Said plates are provided with the intake or outlet ports 20. The outlet ports, for example, are of such shape as to provide a gradually increasing outlet for the inwardly moving lobes to thereby permit of gradual passage of air from the high pressure outlet to the low pressure chambers between the oncoming rotors. As the opposed rotors progress toward each other to squeeze the entrapped low pressure air through the ports 20, the ports widen out so as to give ample freedom for the outward forcing of air from between the lobes. Thus the shape of the ports is such that as the lobes move into discharge position there is only a small opening to permit the pressure to be equalized gradually, followed by successively larger opening to permit of increased amounts of air to be discharged.

A shown in Fig. 2, but particularly illustrated in the diagrammatic drawing of Fig. 4, the cylinder bore for each rotor is formedconcentric with the axial center of the rotor about the intermediate portion thereof extending from the point tion of the housing wall.

A to the point B, the center of the rotor being indicated at C and the radius of the bore being greater radius E" with a radial center F ofiset from the axial center of the rotor toward the center of the unit. This eccentric portion of the bore merges with the portion A, B and extends to thecenter of the inlet and outlet openings. These concentric and eccentric bores, the latter with a greater radius than the former, are duplicated indicated by dotted lines gradually receding from.

the wall of the housing to open a passage from the high pressure area of the outlet to the lowerpressure area of the oncoming pocket between the rotors. This passage gradually increases in area to thereby permit a gradual approach to equalized pressure as the oncoming lobes approach the ports 20. The increase in the passage is indicated by the spacing between the path of the rotor lobes, as shown in dotted lines, and the eccentric por- Therefore, from the time'the lobes pass the point B until they mesh with the opposed lobes, the pressure in the oncoming pocket increasingly approaches the pressure (or back pressure) of the outlet opening. This gradual equalization of pressure thereby prevents the sudden inrushing of air due to back pressure, so that no pulsations or objectionable noise results therefrom.

The shape of the ports materially contribute to this effect and in fact, the shape of the ports 20 will have a similar effect even without the eccentric bores of the housing. This is due to the fact that with the angular and tapering ports, equalization of pressure takes place gradually as the lobes pass the angularly disposed ports from the reduced end thereof, as indicated by the arrows in Fig. 3. Similarly, this effect is likewise obtained with the usual full size ports by reason of the eccentrically bored housing due to the gradualseepage past the lobes as they leave the housing wall in entering the eccentric portion thereof.

The aboveinvention has been particularly described as applied to a fluid pump in the form of a "Root blower adapted for use'as a supercharger. However, the invention is equally applicable to any other type of pump. Likewise, whereas reference has been particularly made to the effect by pressure equalization at the exhaust opening, it is equally applicable at the intake opening under reverse pressure conditions. The invention, having been herein described as applied to air pressures, is similarly applicable to other gases and liquids.

The invention claimed is:

1. A fluid pump of the Root rotary blower type including a housing formed with opposed bores having inlet and outlet openings and rotors rotatable in each bore having intermeshing lobes forming pockets therebetween, each of said bores having a relieved portion formed adjacent the outlet opening gradually spaced from the outer path of the rotors as they approach the said outlet opening to provide a graduated passage for equalization of pressure between the oncoming pockets of said'rotors and said outlet, said outlet 7 opening comprising a biased port tapered toward the oncoming pockets over which said lobes pass from the narrower to the larger portion thereof to effect a gradually increased communicating area through said port between the pressure side thereof and the oncoming pockets,

whereby totalpressure equalization therethrough will be delayed.

2. A fiuid pump of the "Root" rotary blower type including a housing formed with opposed bores having inlet and outlet openings and rotors rotatable in each bore having intermeshing lobes forming pockets therebetween, each of said bores having a relieved portion formed adjacent the outlet opening and gradually spaced from the outer path of the rotors as they approach the said outlet opening to provide a graduated passage for equalization of pressure between the oncoming pockets of said rotors and said outlet opening, said outlet opening comprising a triangular biased port tapered toward the oncomin pockets ,over' which said lobes pass from the narrower to the larger portion thereof to effect a gradually increased communicating area between the pressure side thereof and the oncoming pockets whereby, total pressure equalization therebetween will be delayed.

3. A fluid pump of the Root rotary blower type including a housing formed with opposed bores having inlet and outlet openings and rotors rotatable in each bore having intermeshing lobes forming pockets therebetween, each of said bores having an intermediate portion of their walls formed concentric with the axial center of their respective rotors and of substantially the radius thereof, said concentric portions spanning the pocket between lobes for sealing the same, an eccentric relieved-portion of greater radius and having the center thereof oriented toward the center of the housing formed in said bores adjacent the outlet opening, and a biased port tapered toward the oncoming pockets comprising the outlet opening over which said lobes pass from the narrower to the larger portion ereof to efiect a gradually increased commit ating area between the pressure side thereof and the oncoming pockets whereby total pressure equalization between the oncoming pockets and the pressure side of the ports will be delayed and the pressure in said pockets will gradually approach the pressure of the outlet opening.

4. A fluid pump of the "Root rotary blower type including a housing formed with opposed bores having inlet and outlet openings and rotors rotatable in each bore having intermeshing lobes forming pockets therebetween, each of said bores having an intermediate portion of their walls formed concentric with the axial center of their respective rotors and of substantially the radius thereof, said concentric portions spanning the pocket between lobes for sealing the same, an eccentric relieved portion of greater radius and having the center thereof oriented toward the center of the housing formed in said bores adjacent the outlet opening, and a plurality of triangular biased ports tapered toward the oncom- 5. A fluid pump of the character described comprising a housing having a pair of opposed bores with an inlet opening on one side and an outlet opening on the other side thereof, said openings being located intermediate said bores, a pair of opposed rotors, means for driving said rotors in opposite directions within said bores respectively, said rotors including intermeshing pocket-forming lobes to effect a fluid seal with a portion of said bores respectively, each of said bores having an intermediate portion of their' walls formed concentric with the axial center of their respective rotors and substantially the radius thereof, said concentric portion spanning the pocket between lobes for sealing the same, an eccentric relieved portion of said bores formed adjacent the inlet and outlet openings with their walls of greater radius and having the center thereof oriented toward the center of the housing, whereby said lobes will recede from the housing as they approach said openings to gradually permit equalization of pressure between the oncoming pockets and openings, and a plurality of triangular biased ports tapered toward the oncoming pockets forming said inlet and outlet openings over which said lobes pass from the narrower to the larger portion thereof to effect a gradually increased communicating area between the pressure side thereof and the oncoming pockets for delay of said pressure equalizazation therebetween.

6. A fluid pump of the Root rotary blower type including a housing formed with opposed bores having inlet and outlet openings and rotors rotatable in each bore having intermeshing lobes forming pockets therebetween, said outlet opening comprising a triangular biased port tapered toward the oncoming pockets over which said lobes pass from the narrower to the larger portion thereof to effect a gradually increased communicating area between the pressure side thereof and the oncoming pockets whereby total pressure equalization therebetween will be delayed.

7. A fluid pump of the character described comprising a housing having a pair of opposed bores with an inlet opening on one side and an outlet opening on the other side thereof, said openings being located intermediate said bores, a pair of opposed rotors, means for driving said rotors in opposite directions within said bores respectively, said rotors including intermeshing pocket-forming lobes to effect a fluid seal with a portion of said bores respectively, and a plurality of triangular biased ports tapered toward the oncoming pockets forming said inlet and outlet openings over which said lobes pass from the narrower to the larger portion thereof from the base to the apex thereof to effect a gradually increased communicating area between the pressure side thereof and the oncoming pockets for delay of said pressure equalization therebetween.

KURT A. BEIER.

REFERENCES CITED UNITED STATES PATENTS Number Name I Date 625,785 Morgan May 30,1899 1,769,647 Press July 1, 1930 FOREIGN I PATENTS Number Country Date 94,751 Germany 1896 142,858 Great Britain 1920 282,752 Great Britain May 31, 1928 773,646 France Sept. 3, 1934 

